Method of operating a buffer memory to provide a trigger pattern by storing a trigger code in preselected areas of the buffer memory

Abstract

Selected memory locations of a buffer memory having an m x n address space are loaded each with a trigger code. First and second data words, in bits and n bits respectively, are used to read the numerical value stored at a memory location of the buffer memory. If the numerical value bears a predetermined relationship to the trigger code, a predetermined response signal is generated.

I claim: 
     
       1. A method of operating a buffer memory to generate a trigger when a waveform in the form of pairs of data words falls outside a defined region, the buffer memory having an array of memory locations defined by first and second address words, each memory location storing a numerical value, said method comprising the steps of: (a) loading selected memory locations of the buffer memory corresponding to the defined region with a trigger code,   (b) receiving a first data word and a second data word from each pair of data words,   (c) reading from the buffer memory the numerical value stored at the memory location whose first and second address words are defined by the first and second data words, and   (d) generating the trigger when the numerical value read in step (c) bears a predetermined relationship to said trigger code.   
     
     
       2. The method according to claim 1 further comprising the steps of: incrementing the numerical value read in step (c) by a selected amount when the numerical value does not bear said predetermined relationship to said trigger code, and   writing the incremented numerical value back to the memory location that was read in step (c).   
     
     
       3. The method according to claim 1 further comprising the steps of: (e) reading the numerical value from each memory location of the buffer memory,   (f) decrementing each numerical value that does not bear the predetermined relationship to the trigger code by a selected amount, and   (g) writing the decremented numerical values back to the respective memory locations.   
     
     
       4. The method according to claim 1 wherein the buffer memory has at least two coextensive arrays of memory locations, the locations of each array being defined by the first and second address words, and step (b) comprises the steps of: (b)(i) acquiring the first and second data words from an input signal, and   (b)(ii) employing the first data word and the upper m bits of the second data word to determine the first and second address words to select a memory location in each of said coextensive arrays,   step (c) comprises the step of reading the numerical values from the selected memory location in each array, and   step (d) comprises the steps of: (d)(i) comparing the numerical values from the selected memory locations with the trigger code, and   (d)(ii) employing the lower p bits of the second data word to select one of the results of the comparing step to determine whether said trigger should be generated.     
     
     
       5. A method of operating a buffer memory that has a multiplicity of memory locations in an address space having a first dimension and a second dimension, each memory location storing a numerical value, said method comprising the steps of: (a) loading the memory locations within a selected area of the address space with a trigger code,   (b) acquiring a succession of pairs of data words from an input signal, each pair being composed of a first data word and a second data word, the range of the first data word being equal to at least the range of the first dimension of the address space and the range of the second data word being equal to at least the range of the second dimension of the address space,   (c) for each pair of data words, (i) reading from the buffer memory the numerical value stored at the memory location whose address in the first dimension of the address space is defined by a first address word and whose address in the second dimension of the address space is defined by a second address word, the first and second address words being related in a predetermined fashion to the first and second data words,   (ii) comparing said numerical value with said trigger code,   (iii) generating a predetermined response signal when said numerical value bears a predetermined relationship to said trigger code, and   (iv) incrementing said numerical value by a predetermined amount and writing the incremented numerical value to the memory location that was read in step (c)(i) when said numerical value does not bear the predetermined relationship to said trigger code,     (d) subsequently generating the first and second address words independently of the first and second data words, and   (e) for the first and second address words (i) reading from the buffer memory the numerical value stored at the memory location defined by the first and second address words,   (ii) writing the numerical value unchanged back to the memory location read in step (e)(i) when said numerical value bears the predetermined relationship to said trigger code, and   (iii) decrementing the numerical value by a selected amount and writing the decremented numerical value back to the memory location read in step (e)(i) when said numerical value does not bear the predetermined relationship to said trigger code.     
     
     
       6. The method according to claim 5 further comprising before step (a) the step of defining said selected area of the address space. 
     
     
       7. Buffer memory apparatus for generating a trigger when a waveform in the form of pairs of data words falls outside a defined region comprising: a multiplicity of memory locations occupying a two-dimensional address space and each storing a numerical value,   means for defining an area of the address space corresponding to the defined region and loading the memory locations within the defined area each with a trigger code,   means for receiving the pairs of data words, each pair having a first data word and a second data word,   means responsive to each pair of data words from the receiving means for reading from the buffer memory the numerical value stored at the memory location whose address is defined by a first address word and a second address word related in a predetermined fashion to the first and second data words, comparing the numerical value read from the buffer memory with said trigger code, and generating the trigger when said numerical value bears a predetermined relationship to said trigger code.